Alternatives to Glass for Wine Packaging: Can Plastic Perform?

In this age of environmental awareness, the wine industry is frequently tuned in to environmentally-friendly alternatives to the status-quo.  For example, wineries have been known to recycle their wastes for animal feed, fertilizer, or even pharmaceuticals, in addition to reevaluating how their wines are distributed to customers.  One side of the wine business that is starting to garner more attention is the packaging aspect.  Wine is not only packaged in glass bottles, but also in plastic bags, plastic bottles, and even cans.

Studies and speculation have shown, however, that the type of packaging used may influence the overall quality of the wine, which ultimately relates to the gas exchange between the wine and the atmosphere through the packaging.  The oxidation of wine, while important to the overall character of the wine at certain rates, may cause a loss of aromatic quality, the degradation of anthocyanins and tannins, and the appearance of a brown precipitate if too much oxygen is present.

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In recent years, a particular type of plastic has been developed to potentially help reduce the amount of oxidation in wines caused by poor packaging materials.  PET, otherwise known as polyethylene terephthalate, belongs to the polyester family, and has been developed for preservation of foods and beverages (sodas, juices, water, and now wine).  Chemically, PET is a combination of ethylene glycol and terephthalic acid, which form a polymer chain.  This chain is then broken down into small pellets, then heat applied to create a liquid which may then be formed into any desired shape.  Advantages to this type of material are cited as being transparent, low cost, and strength.  As a result of this technology, PET has been considered a potential acceptable replacement for glass, available in both single-layer and multi-layer forms.

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The PET multi-layer form was developed in an attempt to improve the gas barrier properties of the container, and consists of a three layer structure of PET – Gas Barrier Resin – PET, or a five layer structure of PET – Gas Barrier Resin – PET – Gas Barrier Resin – PET.  The gas barrier resin could be created using many compounds, with one example being an ethylene-vinyl alcohol copolymer and MXD6 nylon.  One potential environmental concern with the multi-layered PET containers is that the present of the polymers in the different layers make recycling more difficult and more expensive.  Boxed wine (i.e. Bag in Box®) uses similar technologies as PET, with multiple layers as described above.  To protect the bag, a cardboard box is employed.  Some studies have shown that PET bottles are capable of storing a wine up to 7 months, and are successful in slowing down the transfer of oxygen that would otherwise cause wine quality decay.

The study reviewed today, which is currently available only in online form until the publication comes out in January 2012, aimed to study the decay of quality in both white and red wines in different packaging types (glass bottles, PET multi-layer bottles, PET mono-layer bottles, and Bag in Box®) and different volumes (18.5cL and 75cL for bottles, and 300cL for Bag in a Box®).

Methods

The wines sampled were both red and white Bordeaux blends from the 2008 vintage.  All bottling occurred via standard approved methods, and a screw cap was the chosen closure.

For the packaging, glass bottles, mono-layer PET (0.3mm thickness), multi-layer PET (0.4mm thickness), and Bag in Box® were used.

All wine samples were stored upright at 20 degC for 18 months.

Oxygen levels were measured using a chemical electrode oxygen Probe.  Carbon dioxide levels were measured using the multiple expansion method.  The following standard enological parameters were also measured: titratable acidity, volatile acidity, alcohol content, pH, microbiological characteristics, color characteristics, and sulfur dioxide.

Thiols were measured using gas chromatography and mass spectrometry.

For each treatment (i.e. each wine in each packaging type), samples were collected and analyzed just after bottling, and then again at 3, 6, 9, 12, and 18 months.

Sensory analysis of the wines occurred just after bottling, in addition to after 6, 12, and 18 months of aging.  The panel consisted of 25 experts (researchers and PhD students of the faculty of enology at the Université de Bordeaux).  Analysis took place in a standard tasting room with private booths, with wines assessed at 20oC (smell and taste).  For white wines, the descriptors analyzed were limpidity, color intensity, sauvignon character, and oxidative and reduction evolutions.  For red wines, the descriptors analyzed were color intensity, evolution of the color, fruity character, oxidative evolution, reduction, astringency, and bitterness.  All attributes were scored on a scale from 0-5.

Results

White Wine

Oxygen:

  •       The initial concentration of oxygen was 0.73mg/L
  •       For glass bottles and multi-layer PET (75cL), the oxygen content decreased quickly in the first three months, then remained stable and very low.
  •       For multi-layer PET (18.5cL) and Bag in Box®, the oxygen content was around 0.5mg/L.
  •       For mono-layer PET, the oxygen content was high around 1mg/L for the 75cL bottle and 2.5mg/L for the 18.5cL bottle after 12 months.

o   The mono-layer PET bottle allowed oxygen to transfer into the bottle easily, and oxidized the white wine.

o   Bag in Box® and the 18.5cL multi-layer PET bottle displayed oxygen transfer at a rate not as high as the mono-layer PET bottle, however still significant and could alter the sensory characteristics of the wine.

o   Glass and the 75cL multi-layer PET bottles were the best barriers to oxygen for white wines.

Carbon Dioxide:

  •        The initial concentration of carbon dioxide was 0.9mg/L.
  •       Bag in Box® and the 18.5cL mono-layer PET bottle had a low CO2 concentration of <0.5g/L.
  •       For all other packaging types, the CO2 concentration ranged from 0.5g/L to 1g/L.
  •       CO2 concentrations were relatively constant for glass bottles and the multi-layer PET bottles.

Sulfur Dioxide:

  •       Note:  if free SO2 drops below 10mg/L, white wine will be subject to oxidation and increased browning.
  •       Glass bottles and multi-layer PET bottles contained over 10mg/L free SO2 after 12 months of storage.
  •       The other packaging types had free SO2 levels ranging from 3 to 7mg/L.

OD420:

  •        Note: a decrease in SO2 levels will accelerate the oxidation of a white wine and change the color hue.
  •       The 18.5cL mono-layer PET bottles resulted in clearly oxidized wine after 12 months in storage (OD420 value of 0.155).
  •       Wine from both the 75cL mono-layer PET bottles and the 18.5 multi-layer PET bottles had OD420 values reaching 0.120, which indicates oxidation.
  •       For all other packaging types, there was no sign of oxidation and wine color appeared normal after 18 months of aging.

Volatile Compounds & Oxidation Markers:

  •       3-sulfanylhexan-1-ol decreased in all packaging types after 6 months of aging.
  •       Glass bottles tended to preserve 3-sulfanylhexan-1-ol levels better than the other packaging types.
  •       Choice of packaging influenced the dissolved oxygen level in the bottles and also the redox potential of the wine.
  •       There was an increase in oxidation markers:

o   Levels of methional, phenylacetaldehyde, and sotolon were found from highest to lowest in the 18.5 mono-layer PET, 75cL mono-layer PET, Bag in Box®, 18.5cL multi-layer PET, and 75cL multi-layer PET bottles.

o   With these packaging types, oxidation markers were found to be above their perception thresholds.

  •       Only aging in the 75cL glass bottles appeared to keep the wine free from oxidation markers.

Sensory Analysis:

  •       Sensory analysis indicated differences in sensory attributes depending upon which type of packaging was used.

o   After 6 months, sauvignon character and color intensity was altered in the mono-layer PET, 18.5cL multi-layer PET, and Bag in Box® bottles.  This same result was found at 12 and 18 months (and included all mono- and multi-layer bottle types).

  •       White wine sensory quality is highly influenced by packaging type, and is noticeable by 6 months of aging.

Red Wine

Oxygen:

  •       Only Bag in Box® showed increased levels of dissolved oxygen.
  •       All other packaging types showed normal levels of dissolved oxygen for red wine.

Carbon Dioxide:

  •       The initial level of CO2 after bottling was 0.9g/L.
  •       There was a linear decrease of CO2 in the glass and multi-layer PET bottles over time.

o   Since CO2 cannot permeate through glass, this decrease was due to gas transfer through the screw cap closure.

  •       The CO2 content was higher in glass bottles than all other packaging types, and was still at acceptable levels after 18 months of aging.
  •       For Bag in Box®, the CO2 levels quickly decreased in the first three months of aging, however remained stable through the rest of the experiment (0.5g/L).

Sulfur Dioxide:

  •       There were decreases in the SO2 levels of wine in all packaging types, though the decrease was less for the glass bottles.
  •       SO2 levels in all packaging (except the glass bottles) was 10mg/L after 18 months of aging (this value is low).

OD420:

  •       The color of the red wines were not influenced by the packaging type.

Sensory Analysis:

  •       There were no differences in any of the sensory attributes for any of the red wines, regardless of packaging type.

Conclusions

Overall, I thought the results of this study were very interesting and potentially important for finding alternative packaging for wine that is both environmental friendly and able to preserve the quality of the wine.   It seems as though PET bottles (particularly mono-layered PET bottles) were the less effective in preserving the quality of white wines, as a result of rapid oxidation.  The sensory analysis also showed marked decreases in wine quality of bottles created with any packaging material other than glass.  I believe based on these results, it’s safe to say that the standard glass bottle is still the best vesicle for storing white wines for over 6 months of time.

The twist in this study, to me, came with the analysis of the red wines.  According to the results of this study, no matter what type of packaging used, there were no degrading effects on the overall quality of the red wine.  A glass bottle? A plastic bottle? A Bag in Box®?  Based on what was found in this study, it doesn’t matter; the wine should taste just fine!  Perhaps I’m just naïve, but that blew my mind a little bit!

Of course, more research needs to be done on more varietals of wine, to confirm if all white wines are sensitive to packaging type and all reds unfazed.  All in all, I found the results of this study very interesting—what I expected for whites, but totally out of left field for the reds!

What do you all think about this?  I’d love to hear your thoughts!  Please feel free to comment below!

Source:  Ghidossi, R., Poupot, C., Thibon, C., Pons, A., Darriet, P., Riquier, L., De Revel, G., Mietton Peuchot, M. 2012. The influence of packaging on wine conservation. Food Control 23: 302-311.

DOI: 10.1016/j.foodcont.2011.06.003
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!

11 comments for “Alternatives to Glass for Wine Packaging: Can Plastic Perform?

  1. Becca
    December 12, 2011 at 2:56 pm

    Great right up and interesting results. One quick question, was it stored at 200 C or 20 deg C? It seems unlikely that it is 200C and if it is, what is the reasoning for such a high temperature?

  2. Becca
    December 12, 2011 at 2:57 pm

    *Great write up. More coffee please.

  3. December 12, 2011 at 3:10 pm

    Thanks for reading, Becca! The temp was 20 deg C. It appears as though when copying from Word to the blogging platform, the formatting wasn't able to retain the superscript in the degree symbol (thus making it appear at the same level as the 0 in 20). I'll go back and change the degree symbol to the word "deg" to avoid any more confusion! Thanks for pointing it out!

  4. SUAMW
    December 12, 2011 at 7:17 pm

    I had purchased several of these bag-in-bottle wines (white ***and red***) and tasted them over the course of a week.
    The wines oxidized within days. I am not sure if this was due to O2 ingress across the plastic or if air simply got into the bag when the spout was opened for a a pour.

  5. December 13, 2011 at 2:34 pm

    My guess is that the oxygen got into the bag via the spout. That's one thing this study did not test–what happens to the wine after you've opened it. They just tested the wines after opening it once. I also wonder if the quality of wine to start with affects the results at all.

  6. Rachel
    December 13, 2011 at 6:33 pm

    Plastic in any form can not be considered "environmentally friendly." It can be difficult to recycle into other products, should recycling even be attempted by the consumer, and even when recycled, it never actually biodegrades and breaks down. We have a plastic garbage patch that is literally the size of Texas in the North Pacific gyre compromising sea life all the way up the food chain (including us), and calling packaging that will eventually contribute to such things "environmentally friendly" is a gross misnomer.

  7. Rachel
    December 13, 2011 at 6:33 pm

    Many plastics contain compounds, endocrine disruptors for example, that are harmful to one's health when leached into food and drink products. It does not appear that this study addressed any health concerns created by toxic leaching by testing for any harmful compounds over the course of the study. The more promising study would be regarding wine in a can, which has more promise for a.) reducing shipping weight; b.) storing wine optimally without affecting its major characteristics; c.) not leaching harmful chemicals into the beverage; and d.) being much easier to recycle than plastic and truly biodegradable. All of this assumes that the can is not lined with some sort of plastic, as many cans are. In the meantime, though glass bottles are heavy, they are the more environmentally friendly choice as they are easy to recycle and will biodegrade eventually.

  8. December 13, 2011 at 6:41 pm

    Great points Rachel! Thank you for leaving your comments! I also found it interesting that the authors of this study would assume plastic would be more environmentally friendly than glass. I think their only basis for that statement was that the overall volume would be less than that of glass (which we both know should not be the only determinant for being environmentally friendly).

    At least based on the results, it appears as though glass is the best option for storing wine anyway, so hopefully the market won't soon be inundated with more plastic vessels.

    I am also very curious about the wine-in-a-can option. Just today I shared a link of Facebook (www.facebook.com/TheAcademicwino)” target=”_blank”> ” target=”_blank”>(www.facebook.com/TheAcademicwino) and Twitter (@TheAcademicWino) about companies already doing this, but I've yet to find any scientific studies looking at their effectiveness as wine storage vessels. I'm sure someone out there is working on it, and be sure to keep a look out here on my site when it gets published and I present the results!

  9. Rachel
    December 14, 2011 at 3:06 am

    I would think that cans would only work for short-term storage (i.e., cheap, lower-quality "drink now!" wines), not long-term storage. I am reminded of a recent article I read (http://naturalsociety.com/top-7-supermarket-foods-to-avoid/)” target=”_blank”> http://naturalsociety.com/top-7-supermarket-foods-to-avoid/)” target=”_blank”>(http://naturalsociety.com/top-7-supermarket-foods-to-avoid/) that referenced canned tomatoes as a food to avoid because of the BCA used in the plastic lining of the can. I believe some cans are lined with plastic to prevent the content's acidity from eating away at the can (not entirely sure about that), but the more acidic the contents are, the more chemicals leach into them. I would think a similar phenomenon would hold true with wine. Therefore, to avoid the same pitfalls of using plastic as wine packaging, one would need to use a non-plastic-lined can, but then the acidity of the wine may break down the metal. Any one else have further info on this?

  10. December 14, 2011 at 9:45 pm

    I agree with your thoughts, Rachel. I would guess that unless the cans were lined in someway (which would negate the "environmentally-friendliness" purpose of the can), they wouldn't be very effective as long-term storage vessels. I encourage anyone else with thoughts on this to chime in as well!

  11. Patrick
    June 21, 2012 at 11:40 am

    I note that other comments on this article were made a long time ago but if anyone is still interested in this subject, I offer this. As observed basically the red wines held up just fine over a very long period regardless of the packaging used and the white wines did fine in 3L BIB & 75 cl glass bottles (but not for PET or 37.5 cl glass bottles) during what would normally be an acceptable shelf life for the industry. This study could almost be used to promote BIB wines (despite its financing entirely by the glass bottle maker Owens Illinois) but there were a number of methodological flaws that undermine the credibility of any conclusions.

    The initial free SO2 levels used were not representative of oxygen sensitive white wines packed in BIB in Southern France (35 mg/L of free SO2 is about 10 mg/L less than common representative levels actually practiced) and the fact that CO2 levels for the white BIB wine increased between 3 and 9 months indicates that they likely had some microbiological contamination (probably as a result of the non-representative filling process used) but probably the most blatant protocol failure was that apparently they did even measure Total Package Oxygen or TPO (headspace + DO) in the wine upon filling – yet this is one of the most important determinates of wine shelf-life. Since TPO was not even measured, any shelf-life evaluation (or comparisons) of the package become meaningless and this is true for glass, PET or BIB. It is a disappointment that the authors failed to even mention in the study that they "forgot" to measure what is perhaps the most important variable. Some vague statement at the end such as "for Bag in Box recipients, these results should be interpreted taking account of the semi-automatic filling method used", does not issue a fair warning about how the study was conducted and how tenacious the results really are. Important study limitations are to clearly stated and and this was not done here.

    Despite the flawed methodology adopted, as mentioned, the BIB wine actually held up very well over what could be considered as current, real life shelf-life requirements but when adopting an 18 month test period the authors did not even refer to the all-important concept of whether or not the observed shelf-life met normal distribution requirements for each package type. In their conclusions they said that "analysis revealed significative differences in terms of oxidative evolution, sauvignon character, and colour intensity over a short conservation period (12 months)" and that "For red wines, no significant differences were measured in O2, CO2 and SO2 content in the different packaging configurations" (apparently over the entire period of the study) but since when is holding up for 12 months for white wines defined as "short" (in the BIB world) since almost all BIB wine is consumed within 6 months of fill? Given the filling conditions, microbiolical contamination and beginning free SO2 level, I was really surprised that it kept so well for so long. In reading the article, one could be led to believing that there was a problem with BIB wine conservation when there was not. Again, the ending remark about "when selecting packaging materials…full account should be taken of …the type of distribution envisaged." is not explicit. Why did the study authors not state clearly in the conclusion that the BIB wines held up perfectly well during their normally expected shelf-life? This lack of clarity was, for me, misleading and suggests unscientific bias in favor of the project's sponsor.

    Having said this, I have even seen worse shelf life studies. I saw an article in a North American food science journal that drew comparative results regarding different BIB packaging but did not even fill the packages (that were compared) with the same wine! Goes to show you (again) that being published in a scientific journal is no guarantee of quality in the same way that filling a bad wine in a great package will not improve it. I would not classify the ISVV study as totally junk science but it is not very good and hopefully more qualified and independent scientists will undertake new research on this very important subject.

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